Bearing and a table for linear sliding motion

ABSTRACT

According to a bearing and a table for linear sliding motion according to the invention, a sliding table is formed of a plurality of divided blocks which are aligned in one row and have load rolling surfaces on which rolling members rolls. By arbitrarily choosing a number of the divided blocks, a number of the load rolling members can be facilely increased depending on a size of the table to be linearly guided. Therefore, waving of the slide members can be minimized, and linearity of the movement thereof can be improved.

TECHNICAL FIELD

The present invention relates a bearing and a table for linear slidingmotion for linearly guiding a movable object to be slid, for example, ina slide component for machine tools such N.C. machines or industrialrobots.

BACKGROUND ART

A conventional bearing for linear sliding motion of a type describedabove generally has a construction shown in FIG. 17. Specifically, it isformed of a track bed (or track member) (b) having rolling surfaces (b1)on which rolling members (a) such as balls roll in an axial direction; aslide bed (or slide member) (c) having load rolling surfaces (c1), whichcooperate with the rolling surfaces (b1) to hold the rolling members (a)therebetween, and no-load rolling apertures (c2) corresponding to theload rolling surfaces (c1); and covers (d) for coupling and connectingthe load rolling surfaces (c1) and the no-load rolling apertures (c2) toform endless paths for the rolling members (a). In this construction,the rolling member (a) rolls through load regions between the rollingsurfaces b1 of the track member (b) and the load rolling surfaces (c1)of the slide member (c), whereby the slide bed (c) can linearly movealong the track member (b) with a remarkably small frictionalresistance.

A table for linear sliding motion, which supports a machine tool or awork for guiding them, generally has a construction shown in FIGS. 18and 19, in which a plurality of track members (b) (two in the Figure)used for the bearings for the linear sliding motion are disposed on afixing portion (e), and a plurality of sliding members (c) (two in theFigure) for carrying a table (f) are assembled to each track bed with aspace between one another.

However, such bearings for the linear sliding motion have followingdisadvantages with respect to the motion of the slide members due to itsconstruction.

First, minute vibration called as "waving" is generated in the slidemembers. In the bearing for the linear sliding motion including therolling members which circulate and perform an endless movement for theslide member, the rolling members are generally in preloaded conditionswhen they roll through a load region in order to increase rigidity ofthe slide member with respect to the track member and prevent rattlingthereof. Therefore, when the rolling members are forcedly entered intothe load region or released from the load region, the slide memberminutely deviates in vertical or lateral directions, which causes theminute vibration, i.e., waving during the movement of the slide member.

A second disadvantage relates to a linearity of a motion of the slidemember. It is ideal for the slide bed to move linearly with respect tothe fixing portion on which the track member is disposed. However, themotion thereof is inevitably affected by a mounting accuracy of thetrack member to the fixing portion and a machining accuracy of therolling surfaces, and thus it is very difficult in practice to obtain ahigh linearity of the movement. If it is attempted to obtain the desiredlinearity of the movement by increasing the mounting accuracy of thetrack member and the machining accuracy of the rolling surfaces,disadvantages such as high costs and low productive efficiency will becaused. Therefore, in view of the above, the linearity of the movementcan be improved only to a restricted extent.

The disadvantages of the motion of the slide member described above forman important factor which cannot be overlooked in machine tools or thelike which are guided by the bearings for the linear motion duringmachining operations, because the waving of the slide members or theinsufficient linearity of the movement causes deviation of the tools ofthe machine tools, and thus directly affects the machining accuracy ofthe products.

However, in the recent industrial application, demands for higheraccuracies in various products, and thus demands for higher machiningaccuracies have been increased in the machines and apparatuses such asmachine tools for machining these products.

Accordingly, the bearings for the linear sliding motion for performinglinear guiding in various machines and apparatuses have been required toprevent the waving during movement or travelling of the slide beds andto improve the linearity of the movement.

On the other hand, with respect to the tables for the linear slidingmotion, reduction of costs has been attempted by minimizing thicknessesof tables which are mounted on the slide members in the recent years.However, this adversely affects the rigidity, and specifically, this maycause deflection or the like in the tables which may reduce themachining accuracies of machine tools mounted thereon.

In view of the above demands and problems, it is an object of theinvention to provide a bearing for linear sliding motion, which canminimize the waving of the slide member and improve the linearity of themovement.

Another object of the invention is to provide a table for linear slidingmotion which allows machining with a high accuracy by a machine orapparatus such as a machine tool mounted thereon.

DISCLOSURE OF THE INVENTION

The inventor of the invention and others have earnestly studied toachieve the objects described above, and found that, as a number ofrolling members which roll through a load region increases, a wavingvalue of a slide bed decreases and also a linearity of a movement isimproved. Based on this, with respect to a table for linearly slidingmotion, a slide member having a length which is increased to a maximumallowable extent and corresponds to a size of a table for linear slidingmotion may be manufactured and attached to a lower surface of the table,whereby the table for the linear sliding motion can have the wavingvalue and linearity for the movement which are improved as compared withthe prior art.

However, since tables have various sizes depending on machines andapparatus mounted thereon, it is not preferable, in view of productiveefficiency, to manufacture slide members of various sizes in accordancewith user's orders.

In view of this, the inventors and others have further studied anddevised the present invention.

A bearing for linear sliding motion of the invention comprises a trackbed provided with rolling surfaces for rolling members such as balls orrollers extending in a lengthwise direction; a slide member formed of aplurality of divided blocks which are provided with load rollingsurfaces cooperating with the rolling surfaces to hold the rollingmembers therebetween, said divided blocks being joined together tocontinuously connect the load rolling surfaces; and rolling membercirculating means which connects opposite ends of the continuouslyconnected load rolling surfaces to form an endless circulation path forthe rolling members.

A table for linear sliding motion of the invention comprises a trackmember provided with rolling surfaces for rolling members such as ballsor rollers extending in a lengthwise direction; a slide member formed ofa plurality of divided blocks which are provided with load rollingsurfaces cooperating with the rolling surfaces to hold the rollingmembers therebetween, said divided blocks being joined together tocontinuously connect the load rolling surfaces; rolling membercirculating means which connects opposite ends of the continuouslyconnected load rolling surfaces to form an endless circulation path forthe rolling members; and table for mounting a movable member to beguided linearly, said table being fixed to the slide member for movementin a lengthwise direction of the track member.

According to the subject of the invention, in which the slide is formedof divided blocks having the load rolling surfaces and jointed together,a number of the divided blocks may be appropriately varied, and forexample, may be determined in accordance with sizes of the table to belinearly guided.

Further, the divided blocks may be varied with respect to aconfiguration, a number of the load rolling surfaces and a contact angleof the rolling members and others depending on a practical applicationof the bearing, and slide member of a bearing for linear sliding motionmay be utilized.

Although the load rolling surfaces of the divided blocks may be formedby individually applying grinding or the like to the respective blocks,it is preferable to simultaneously form the load rolling surfaces on thedivided blocks, which are fixed to a jig for handling it as onecomponent, in order to improve continuity of the load rolling surfacesof the slide member i.e., an assembly of the blocks.

Various variations such as use of ball tubes may be applied to aspecific construction of the rolling member circulating means, whichserves to scoop and return balls from one end of the continuouslyconnected load rolling surfaces to the other end and cooperates with theload region to form an endless circulation path for the rolling members.

Further, the rolling members may be appropriately selected fromcylindrical rollers, barrel rollers, balls and others.

Generally, so-called crowning may be applied to the load rollingsurfaces of the slide member in order to achieve smooth circulation ofthe rolling members, and specifically, opposite side regions of the loadrolling surfaces may be ground to a relatively large extent as comparedwith a middle region to form sections of the load rolling surfaces ofthe side regions into substantially convexly curved shapes. However, inthe present invention, the construction requires to apply the crowningonly to the load rolling surfaces of the divided blocks (hereinafterreferred to "end blocks") located at opposite ends of the slide member.Therefore, a pair of end blocks to which the crowning is applied may beassembled together with an intended number of divided blocks(hereinafter referred to as "middle blocks") to which the crowning isnot applied. This facilitates manufacturing of the slide member having alength corresponding to the number of the middle blocks.

According to the subject of the invention described above, byappropriately selecting the number of the divided blocks, the slidemember can be facilely manufactured to have a long length correspondingto a movable member such as a table to be linearly guided, and thenumber of the load rolling members which rolls through the load regioncan be increased in accordance with the increase of the length of theslide member.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1 and 2 are a perspective view and a cross section illustrating afirst embodiment of a bearing for linear sliding motion of theinvention, respectively;

FIGS. 3 and 4 are a cross section and a side view illustrating an endblock (middle block) according to a first embodiment, respectively;

FIG. 5 is a rear view of a cover;

FIG. 6 is a cross section taken along line VI--VI in FIG. 5;

FIG. 7 is a cross section taken along line VII--VII in FIG. 6;

FIG. 8 is a perspective view illustrating a guide piece;

FIGS. 9 and 10 are a perspective view and a cross section illustrating atrack members, respectively;

FIG. 11 is a cross section illustrating an endless ball circulation pathin the slide member;

FIGS. 12, 13 and 14 are a perspective view, a top view and a front viewillustrating a first embodiment of a table for linear sliding motion ofthe invention, respectively;

FIG. 15 is a cross section illustrating an endless ball circulation pathfor bearings for the linear sliding motion used in experiments;

FIG. 16 is a cross section illustrating another embodiment of a bearingfor the linear sliding motion of the invention;

FIG. 17 is a perspective view illustrating a bearing for the linearsliding motion in the prior art; and

FIGS. 18 and 19 are a top view and a front view illustrating a table forthe linear sliding motion in the prior art for comparison, respectively.

DESCRIPTION OF THE REFERENCE NUMERAL

1: track bed, 2: slide bed, 2a: end block (divided block), 2b: middleblock (divided block), 3: cover (rolling member circulating means), 4:ball (rolling member), 11: rolling surface, 24: load rolling surface

DETAILED DESCRIPTION OF THE INVENTION

A bearing and a table for linear sliding motion of the invention will bedescribed with reference to the accompanying drawings.

FIGS. 1 and 2 illustrate a first embodiment of the bearing for thelinear sliding motion of the invention. The bearing is formed of a trackmember 1 mounted on a stationary or fixing portion, a slide bed 2disposed over the track member 1, a pair of covers 3a and 3b (rollingmember circulating means) attached to opposite ends of the slide member2, and a large number of balls (rolling members) which bear a loadbetween the track member 1 and the slide member 2.

As shown in FIG. 1, the slide member is formed of end blocks 2a locatedat opposite ends thereof and two middle blocks 2b disposed therebetween.These blocks are connected by connecting bolts 51 through connectingplates 5. As shown in FIGS. 3 and 4, each of the blocks 2a and 2b has abase 21a (21b) and a pair of wings 22a (22b) extending downwardtherefrom to form an inverted C-shaped section, and is provided at aninner surface of each wing 22a (22b) with vertically spaced two grooves23a (23b) extending in an axial direction. In each groove, there isformed a load rolling surface 24a (24b) having a curved section of aradius of curvature larger than a radius of a ball 4 which rollsthereon. Both the sleeves 22 are provided with no-load rolling apertures25a (25b) which form parts of rolling member circulating means andrespectively correspond to the load rolling surfaces 24a (24b). Uppersurfaces of the base 21a (21b) form mounting surfaces 26a (26b) on whicha movable member such as a table is mounted, and are provided withtapped bolt holes 27a (27b) engaging mounting bolts (not shown). In FIG.3, numerals 28 and 29 indicate ball retainers, which are fixed to thebases 21a (21b) and the wings 22a (22b) by screws (not shown),respectively, and serve to prevent the balls 4 from dropping from thegrooves 23a (23b) on the blocks 2 when the slide bed 2 is removed fromthe track member 1. Numerals 30a (30b) indicate bolt holes engaging thecoupling bolts 51.

In this embodiment, continuity of the load rolling surfaces 24a and 24bof the blocks 2a and 2b coupled together is improved by simultaneouslygrinding the four blocks 2a and 2b to form the load rolling surface 24.That is; the four blocks 2a and 2b are coupled together when fixed to amachine tool, and are handled as one integral slide bed when thegrinding is applied thereto.

Crowning is applied to the load rolling surfaces 24a of the end blocks2a after the grinding so that the balls 4 may be smoothly forced intothe load region and released therefrom. On the other hand, the covers 3are made from synthetic resin and are provided, as shown in FIGS. 5-7,at their inner sides with ball return paths 31 which connect the loadrolling surfaces 24a formed on the end blocks 2a and the correspondingno-load rolling apertures 25a. These ball return paths 31 are formed bysemicircular guide pieces 33 which have guide surfaces 32 continuing tothe load rolling surfaces 24a and are fitted over ball guide grooves 34formed in the covers 33. Numerals 35 indicate through holes throughwhich fixing bolts (not shown) screwed into the end blocks 2 areinserted.

The track member 1 has a rectangular cross-sectional shape as shown inFIGS. 9 and 10 which has opposite sides recessed into trapezoids andalso has recessed right and left shoulders. On inclined surfaces whichare faced obliquely downward and formed by the above trapezoidal as wellas inclined surfaces which are faced obliquely upward and formed by therecessed shoulders, there are provided rolling surfaces 11 whichcorrespond to the load rolling surfaces 24a and 24b of the end blocks 2aand the middle blocks 2b, respectively. Numerals 12 indicate attachingholes through which fixing bolts (not shown) are inserted for engagingthe fixing portion.

According to the bearing for the linear sliding motion of the inventionthus constructed, as shown in FIG. 11, a pair of end blocks 2a and thetwo middle blocks 2b are coupled together to form the long load rollingsurface 24 by the continuous load rolling surfaces 24a and 24b of theblocks 2a and 2b, and also the slide member 2 provided with the no-loadrolling apertures 25 corresponding to the load rolling surfaces 24 areobtained therefrom. Further, by attaching the covers 3 to the end blocks2a, the endless ball circulation paths which connect the load rollingsurfaces 24 and the no-load rolling apertures 25 of the slide member 2are formed, whereby the slide bed 2 shown in FIG. 1 is completed.

FIG. 12 shows a first embodiment of a table for the linear slidingmotion including two sets of the bearing for the linear sliding motionof the embodiment described above. The track member 1 are disposed onthe fixing portion with a predetermined space between one another, and atable 7 is fixed to the slide members 2.

With respect to the manufacturing of the table for the linear slidingmotion shown in FIG. 12, since the number of the middle blocks 2b can beappropriately determined in the bearing for the linear sliding motion ofthe embodiment, the slide members 2 having lengths depending on thesizes of the area in which the slide members 2 are disposed can befacilely manufactured.

Accordingly, it is possible to increase the number of the load balls 4rolling between the load rolling surfaces 24 of the slide members 2 andthe rolling surfaces 11 of the track beds 1 in accordance with the sizesof the table 7, so that waving in the vertical and/or lateraldirections, which may be caused by circulation of the balls 4, can beminimized, and the linearity of the movement can be increased.

Since the lengths of the slide members 2 are increased depending on thesizes of the table 7, a contact area between the slide members 2 and thetable 7 can be increased, so that the rigidity of the table can beincreased, as compared with the conventional bearing for the linearsliding motion shown in FIG. 20.

In order to confirm the effectiveness of the invention, the inventors ofthe application and others have actually determined waving values of thetable for the linear sliding motion shown in FIG. 12. The measuredresults are as follows. For comparison, similar measurement has beenmade with respect to the table for the linear sliding motion employingthe conventional bearing for the linear sliding motion shown in FIGS. 18and 19 (this table will be called as a "comparison example"), and theresult of this measurement also will be described below.

The slide bed 2 used in the experiment is slightly different from thatof the first embodiment in that the slide member 2 is formed of fourconventional bearing blocks 2c coupled together. Therefore, as shown inFIG. 15, the crowning has been applied to the load rolling surface 24cof each block 2. However, other structures such as the load rollingapertures 25c are similar to those of the bearing of the firstembodiment.

With respect to the table for the linear sliding motion of theinvention, variation of the waving values which may be caused by thevarious coupling states between the blocks 2a and 2b and the table 7were determined by measuring the waving values in a case (experiment(1)) in which only the attaching bolts for the bolt holes 27a in the endblocks 2a were fastened and in a case (experiment (2)) in which all theattaching bolts for the bolt holes 27a and 27b in the end blocks 2a andthe middle blocks 2b were fastened (see FIG. 13).

The waving values were determined at points of distances and heights ofA=97 mm, B=107 mm in FIGS. 13, 14, 18 and 19, and C=360 mm. Spacesbetween the track beds in the embodiment and the comparison example areequal to each other, i.e., D=315 mm. The slide bed of the embodiment hasa length of E=341 mm, and the space between the slide members in thecomparison example is 341 mm (F=341 mm).

The waving values obtained from the experiments are as follows.

Experiment 1

vertical direction: 0.11 μm

lateral direction: 0.09 μm

Experiment 2

vertical direction: 0.095 μm

lateral direction: 0.073 μm

Comparison Example

vertical direction: 0.2˜0.25 μm

lateral direction: 0.2˜0.25 μm

As can be seen from the results described above, in the table for thelinear sliding motion using the bearing for the linear sliding motionaccording to the invention has the waving values which are substantiallyhalf or less than those of the comparison example, and thus theeffectiveness of the invention can be confirmed. Further, it has beenfound that the waving values are improved in the bearing for the linearsliding motion according to the invention, if all the blocks c are fixedto the table.

The bearing for the linear sliding motion of the invention is notrestricted to the first embodiment described-above, and, for example, itmay have a sectional configuration as shown in FIG. 16. Structures inFIG. 16 are similar to those described above, except for the sectionalconfiguration of the block 2a (2b), and thus the same reference numeralsare allotted thereto without detailed description thereof.

INDUSTRIAL APPLICABILITY

According to the bearing for the linear sliding motion of the invention,as described hereinabove, the slide member can be constructed bycoupling the divided blocks and thus the number of the load rollingmembers can be facilely increased in accordance with the sizes of thetable to be linearly guided, so that the waving of the slide member canbe minimized and the linearity of the movement can be increased.

According to the table for the linear sliding motion of the inventionwhich employs these bearings, the movable member such as a machine toolmounted thereon can be smoothly and linearly guided with a highlinearity, and thus works can be machined with a high accuracy.

Further, since the table can be supported by the slide members havingthe lengths corresponding to the sizes of the table, the table for thelinear sliding motion can have a high rigidity, whereby the thicknesscan be reduced for achieving low cost.

What is claimed is:
 1. A bearing for linear sliding motion, comprising:atrack member provided with rolling surfaces for rolling members such asballs or rollers extending in a lengthwise direction; a slide memberformed of a plurality of divided blocks which are provided with loadrolling surfaces which in cooperation with said rolling surfaces andsaid rolling members supported therebetween, serve to transfer a loadbetween said slide member and said track member, said divided blocksbeing jointed together to continuously connect said load rollingsurfaces; and rolling member circulating means for connecting opposingends of said continuously connected load rolling surfaces to form anendless circulation path for said rolling members.
 2. A bearing asclaimed in claim 1 wherein said slide member is formed of a pair of endblocks having load rolling surfaces to which crowning is applied, and atleast one middle block disposed between said end blocks.
 3. A table forlinear sliding motion, comprising: a track member provided with rollingsurfaces for rolling members such as balls or rollers extending in alengthwise direction;a slide member formed of a plurality of dividedblocks which are provided with load rolling surfaces which, incooperation with said rolling surfaces and said rolling memberssupported therebetween, serve to transfer a load between said slidemember and said track member, said divided blocks being jointed togetherto continuously connect said load rolling surfaces; rolling membercirculating means for connecting opposing ends of said continuouslyconnected load rolling surfaces to form an endless circulation path forsaid rolling members; and a table for supporting a movable member to beguided linearly, said table being fixed to said slide member formovement in a lengthwise direction of said track member.